A next generation WLAN, IEEE 802.11ax or High-Efficiency WLAN (HEW), is under development. Uplink multiuser MIMO (UL MU-MIMO) and Orthogonal Frequency-Division Multiple Access (OFDMA) are two major features included in the new standard. For both features, however, the Access Point (AP) needs to schedule the transmissions or receptions of multiple users. This requires the AP to have channel status knowledge comprising Clear Channel Assessment (CCA) and buffer status of the user communication stations (STAs).